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Old 12-27-2011, 04:38 PM   #1
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Default PH meter and temperature

I've been playing with the pH meter today during a the mash.

I know you have to cool your sample (as a new electrode is expensive!) but how cool is "cool"?

And what is the probable difference in a sample taken at 50 degrees vs. 75 degrees? Which do you typically record for your "mash pH"?

I hope that makes sense. I'm just trying to figure what the mash pH actually "is" compared to the spreadsheets I've used.

In this case, I have a mash pH of 5.29 at 68.7 degrees.

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Old 12-27-2011, 04:49 PM   #2
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Old 12-27-2011, 06:12 PM   #3
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Most meters say "room temp" is best.

I do know that the further away from a ph of 7, the more temperature effects the reading.

This isn't a bad reference... pH versus temperature

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Old 12-27-2011, 06:27 PM   #4
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I use the temp the meter was calibrated at, which is usually 68-70f. Then I cool the mash sample to that.


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Old 12-27-2011, 06:57 PM   #5
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The standard temperatures are either 20C or 25C (68F to 77F). But, its usually 25C. If you're somewhere close to that range, the difference in pH readings will be minor. We're talking a few hundreths, not tenths so this is a case where you can RDWHAHB and not fret too much about the temp.

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Old 12-27-2011, 08:56 PM   #6
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Quote:
Originally Posted by mabrungard View Post
The standard temperatures are either 20C or 25C (68F to 77F). But, its usually 25C. If you're somewhere close to that range, the difference in pH readings will be minor. We're talking a few hundreths, not tenths so this is a case where you can RDWHAHB and not fret too much about the temp.
Thank you!

One thing I learned today was that by the time 15 minutes elapsed (when I checked the mash pH), and cooled to the correct temperature, it was about 30 minutes into the mash. So, good thing I didn't have to adjust it, I guess.

Is 5.29 a good mash pH at room temp? It seems a bit low, but I guess I'd rather miss low than high.
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Old 12-28-2011, 12:11 AM   #7
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I always thought 5.2 was just about ideal for the average beer.

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Old 12-28-2011, 12:17 AM   #8
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I just got a new hanna ph meter that has atc. Do you really need to cool it if your meter has atc?

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Old 12-28-2011, 12:18 AM   #9
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I always thought 5.2 was just about ideal for the average beer.
Yes, for "mash temp", I think. But for some reason I was thinking I should be at 5.4-5.6 for an ideal mash pH at room temp.
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Old 12-28-2011, 12:32 AM   #10
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I do know that the further away from a ph of 7, the more temperature effects the reading.
A meter has an isoelectric pH at which its response is insensitive to temperature and the design isoelectric pH of a modern electrode is 7. But it is usually specified as 6.5 < pHi < 7.5 and I happen to own a rather expensive electrode with pHi = 8.4. If I relied on ATC to correct electrode responses with a modern meter it would do those corrections based on pHi = 7. I have never seen a meter which allows the user to dial in pHi and part of the reason for this is that it is hard to measure. So with this meter I either have to let the computer do ATC based on its knowledge of the true pHi or take all measurements at close to the same temperature. If I do that the ATC error is small and I think that is just good practice. In most cases pHi is close to 7 but I am living proof that that is not always the case and most users woudn't have a clue as to wheterh pHi is normal or off. My advice is calibrate and measure close to the same temperature. You will get accurate reading by doing so even if pHi is as far off as it is in my electrode.
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